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Soft constraint tools for quality aspects: language, frameworks and aggregation schemes

Santini, Francesco (2009) Soft constraint tools for quality aspects: language, frameworks and aggregation schemes. Advisor: Bistarelli, Prof. Stefano. pp. 288. [IMT PhD Thesis]

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The term “quality” as it is commonly understood in the context of Quality of Service (QoS) is “something” by which a user of the service (in a very large meaning) will judge how good the service is. In this research project we mainly focus our attention to three areas related with QoS: i) Networks, ii) Web Services and iii) Trust Management (TM). As defined in (CNRS98), QoS is “a set of service equirements to be met by the network while transporting a flow”, where a flow is “a packet stream from source to a destination (unicast or multicast) with an associated Quality of Service (QoS)”. To be implemented and subsequently satisfied, network requirements have to be expressed in some measurable QoS metrics: well-known metrics include bandwidth, hops, delay, jitter, cost and loss probability. With Constraint-Based Routing (CBR) (YF03) we refer to a class of routing algorithms that base path selection decisions on a set of requirements or constraints, in addition to the destination. The main objectives are to meet the QoS requirements of applications and to optimize the global network resource usage. Web Services (WS) are maturing as a technology that allows for the integration of applications belonging to different administrative domains, enabling much faster and efficient businessto- business arrangements. A Service Level Agreement (SLA) is an agreement regarding the guarantees of a WS: it defines mutual understandings and expectations of a service between the service provider and service consumers, and clearly involves many QoS indications and requests about the traded service (LJJJP03). Trust and Reputation Systems represent a significant trend in decision support for Internet mediated service provision (JIB07). The basic idea is to let parties rate each other, for example after the completion of a transaction, and use the aggregated ratings about a given party to derive a trust or reputation score, which can assist other parties in deciding whether or not to transact with that party in the future. Trust describes how much the reliability in the service is rated, and therefore we can easily consider it as a QoS feature. The aim of my PhD thesis is to provide expressive means (e.g. languages) in order to model and solve these frameworks with the help of Soft Constraints (Bis04), benefiting from Artificial Intelligence background to tackle this kind of optimization problems. Soft constraints will represent the needs of the parties on the traded resources and the consistency value of the store represents a feedback on the current agreement. Using soft constraints gives to the service provider and the clients more flexibility in expressing their requests w.r.t. crisp constraints, and therefore there are more chances to reach a shared agreement. Moreover, the cost model is very adaptable to the specific problem, since it is parametric with the chosen semiring (Bis04).

Item Type: IMT PhD Thesis
Subjects: Q Science > QA Mathematics > QA75 Electronic computers. Computer science
PhD Course: Computer Science and Engineering
Identification Number: 10.6092/imtlucca/e-theses/24
NBN Number: urn:nbn:it:imtlucca-27060
Date Deposited: 06 Jul 2012 14:42
URI: http://e-theses.imtlucca.it/id/eprint/24

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